<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <button>点我获取数据</button>
    <script>
        let btn = document.querySelector("button");
        btn.onclick = function(){
            //创建ajax
            const xhr = new XMLHttpRequest();
            //打开链接
            xhr.open("GET","/dd");
            //发送
            xhr.send();
            //获取数据
            xhr.onload = function(){
                console.log(xhr.responseText);
            }
        }
    </script>
</body>
</html>